This invention relates to methods and compositions for bonding a fluoropolymer to a substrate.
Fluorine-containing polymers (also known as xe2x80x9cfluoropolymersxe2x80x9d) are a commercially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers and semi-crystalline or glassy fluoropolymers. Fluoropolymers are generally of high thermal stability and are particularly useful at high temperatures. They may also exhibit extreme toughness and flexibility at very low temperatures. Many of these fluoropolymers are almost totally insoluble in a wide variety of solvents and are generally chemically resistant. Some have extremely low dielectric loss and high dielectric strength, and may have unique non-adhesive and low friction properties. Fluoroelastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers such as hexafluoropropylene, have particular utility in high temperature applications such as seals, gaskets, and linings.
Multi-layer constructions containing a fluoropolymer enjoy wide industrial application. Such constructions find utility, for example, in fuel line hoses and related containers and hoses or gaskets in the chemical processing field. Adhesion between the layers of a multi-layered article may need to meet various performance standards depending on the use of the finished article. However, it is often difficult to establish high bond strengths when one of the layers is a fluoropolymer, in part, because of the non-adhesive qualities of fluoropolymers. Various methods have been proposed to address this problem. One approach is to use an adhesive layer or tie layer between the fluoropolymer layer and the second polymer layer. Surface treatments for the fluoropolymer layer, including the use of powerful reducing agents (e,g., sodium naphthalide) and corona discharge, have also been employed to enhance adhesion. In the case of fluoropolymers containing interpolymerized units derived from vinylidene fluoride, exposure of the fluoropolymer to a dehydrofluorinating agent such as a base has been used, as well as polyamine reagents applied to the fluoropolymer surface or incorporated within the fluoropolymer itself.
A multi-layer structure includes a fluoropolymer bonded to a substrate, such as a hydrocarbon polymer. The structure is prepared by exposing a bonding composition to actinic radiation, such as ultraviolet radiation, with optional heating, pressure, or combination thereof, to form the bond. The bonding composition includes a light-absorbing electron donor. The bonding composition may be free of adhesive materials.
In one aspect, a method of bonding a fluoropolymer to a substrate includes providing a bonding composition between a fluoropolymer and a substrate, and exposing the bonding composition to actinic radiation.
In another aspect, a method of bonding a fluoropolymer to a substrate includes treating a surface of a fluoropolymer with a bonding composition, contacting the surface of the fluoropolymer with a surface of a substrate, and exposing the bonding composition to actinic radiation. In certain embodiments, exposing the bonding composition to actinic radiation may occur prior to contacting the surface of the fluoropolymer with the substrate.
In another aspect, a method of bonding a fluoropolymer bonded to a substrate includes forming a mixture of a substrate and a bonding composition, contacting the surface of the mixture with a surface of a fluoropolymer, and exposing the bonding composition to actinic radiation.
In yet another aspect, a treated fluoropolymer substrate suitable for bonding to a polymeric substrate includes a surface exposed to a combination of a light-absorbing electron donor and actinic radiation.
The bonding composition may be provided between the fluoropolymer and the substrate in different ways. For example, a surface of the fluoropolymer may be treated with the bonding composition and the treated surface of the fluoropolymer may be contacted with a surface of the substrate, or a surface of the substrate may be treated with the bonding composition and the treated surface of the substrate may be contacted with a surface of the fluoropolymer. In certain embodiments, a mixture of the fluoropolymer and the bonding composition may be extruded and a surface of the extruded mixture may be contacted with a surface of the substrate. In other embodiments, the substrate or the fluoropolymer may be cast from solution or polymerized from a monomer.
In certain embodiments, the method may include heating the bonding composition after exposure to actinic radiation. The bonding composition may be exposed to actinic radiation through the fluoropolymer.
In another aspect, a composite article includes a fluoropolymer having a surface, a substrate having a surface, and a bonding composition interposed between the surface of the fluoropolymer and the surface of the substrate. In still another aspect, an article includes a fluoropolymer layer laminated to a substrate layer wherein the substrate layer includes a light-absorbing electron donor.
In another aspect, a method of treating a fluoropolymer surface includes applying a fluorinated amine or fluorinated aniline to a fluoropolymer surface, and exposing the bonding composition to actinic radiation.
In another aspect, a composition includes at least one of N-methyl-N-2,2,2-trifluoroethylaniline, N-2,2,2-trifluoroethylaniline, 4-(n-perfluorobutyl)-N,N-dimethylaniline, 4-(pentafluoroisopropyl)-N,N-dimethylaniline, 4-(perfluorotetrahydrofurfuryl)-N,N-dimethylaniline, and diethyl-2,2,2-trifluoroethylamine.
The bonding composition includes a light-absorbing electron donor. The light-absorbing electron donor may be an aromatic amine, an aliphatic amine, an aromatic phosphine, an aromatic thioether, a thiophenol, a thiolate, or combinations thereof. The aromatic amine may be an aniline, such as an N,N-dialkylaniline, an N-alkylaniline, or aniline. The light-absorbing electron donor may have a fluorinated moiety, such as a fluoroalkyl group. The light-absorbing electron donor may be polymerizable. The thiolate can be a salt of a mercapto-containing compound.
The bonding composition may further include an aliphatic or aromatic amine, such as a mono-, di-, or tri-substituted amine, such as an alkylamine, an arylamine, an alkenylamine, or an amino-substituted organosilane, such as an amino-substituted organosilane having a hydrolyzable substituent. In certain embodiments, the bonding composition may include an onium salt. The fluoropolymer may be a perfluorinated polymer, such as a fluorinated ethylene and propylene polymer. The substrate may include an inorganic substrate, such as a metal or a glass, or an organic substrate, such as a non-fluorinated polymer.
The light-absorbing electron donor may reduce the fluoropolymer, for example at a Cxe2x80x94F bond, to facilitate bonding. The bonding process may be a photoinduced electron transfer process.
Bonded multi-layer materials may have combined physical and chemical properties possessed by both fluoropolymers and non-fluorinated polymers, resulting in less expensive, well performing articles. For example, the fluoropolymer component may be used in automotive hose and container constructions, anti-soiling films, low energy surface PSA tapes and coatings for aircraft. The bonding process is a mild photochemical lamination that may promote adhesion between a fluoropolymer and a substrate. The bonding composition may be used to form a composite article having a fluoropolymer cladding on a conductive and lustrous metal to protect it from corrosion, a fluoropolymer cladding on glass fibers to enhance their physical strength and chemical resistance for telecommunication, or a fluoropolymer layer bonded to a hydrocarbon substrate in a multi-layer materials. The ability to affect bonding with actinic radiation may permit photo-imaging/photolithography on perfluoropolymers.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.